As a general method for preparing 3D photographs, there is the indirect method in which a multiple of negatives are prepared in advance for a single object, that has a depth and that comprises a principal object, a foreground and background, using a camera containing more than three lenses, the negatives being repetitively printed for more than three times onto a photosensitive sheet containing a lenticular sheet and the photographic angle being changed for each negative.
FIG. 1 illustrates the 3D photographic method. The figure shows the case of a triple-lens camera consisting of the lenses 1, 2 and 3, in which the arrows marked with L and L' show the spans between the observation points while X and Y show respectively the parallaxes between the principal object 5 and background 4 and the principal object 5 and foreground 6.
For instance, if the principal object 5 and background 4 are compared, there are parallaxes of -X on the first print, 0 on the second print and +X on the third print for each of the photographing stations. If the principal object and foreground are compared, there are parallaxes of +Y on the first print, 0 on the second print and -Y on of the third print. Negatives that have different positions of the images of the principal object, foreground and background are prepared from the photographing stations that are located either on a straight line parallel to the object or a line drawn through the center of the object.
The prepared negatives are projected and printed onto a photosensitive lenticular sheet, which consists of a sheet that acts as a lenticular lens and that is coated on the back side with a photosensitive material, from the side of lenticular lens in the order of photographic stations starting from one negative frame to the end of other frames.
When printing is to be done, a part of the principal object is selected as the key-subject, and exposure is executed with positions adjusted so that the key-subject for the images in each negative are coincident. If printing is done with the photographic angle changed for each negative, the images in each negative become separated into a band pattern by the lenticular lenses, and an image band that has a width in proportion to the photographic angle is repetitively arranged in correspondence with the photographic direction.
The formation of a three dimensional image is explained considering as an example the case of a 3D photograph, which was prepared by a single exposure, one each of the 3-frames of a negative being pictured with a triple-lens camera for 3D use. FIG. 2 illustrates an example of a conventional 3D photograph.
The image band formed on the photosensitive layer as shown in the figure is expanded sideways by the lenticular lens and will be seen as a restored image, and different restored images of the two image bands corresponding to different photographic stations will reach the left and right eye of an observer. A three dimensional view is obtained from the superimposition of different image information reaching the left and right eyes of the observer.
In the figure, the right eye receives the image 2 in the center while the left eye receives the image 1 on the right. The image band 2 covers 9.degree. while the image bands of 1 and 3 each covers 7.degree. of the filed of view, and the three dimensional view is obtained in the 23.degree. viewing region in front of the 3D photograph.
The three dimensional effect will differ depending on which photographic station corresponds to the negative, the restored images of which will reach the left and right eyes of the observer. In the event when the photographic stations are different, namely when two image bands of larger observation spans are combined, the three dimensional effect will improve, but because the spacial parallax of the images that enter the left and right eyes is large, this large difference in the image information received by both eyes will be interpreted either as being out-of-focus or as a wrong vision and causes a degradation in the photographic quality.
Consequently, the printing apparatus is arranged in such a manner as the image bands being seen by both of the eyes are ordinarily those that are printed at the bandwidth and band pattern at the photographic angle for which the combination of neighboring negatives have the least the observation span. In addition, one part of the principal object, which is more important in comparison with the background and foreground objects, is specified as the key-subject, and exposure is performed so that the key-subjects of each of the frames of a negative are coincident.
Contrary to conventional photography, in 3D photography, three dimensional effects are in demand more than such photographic characteristics as the color, contrast and sharpness. In order to obtain the three dimensional effect, although it is appropriate to increase the observation span, when an image with a large observation span enters both of the eyes it is likely that an out-of-focus situation or a wrong vision will occur. In conventional 3D photographic printing apparatuses, to prevent the out-of-focus situation and a wrong vision from occurring, the image band is formed so that a combination of negatives with the least observation span enters the left and right eyes of the observer.
Using a multi-lens compact camera for 3D use where the lens spacing is fixed, and especially when a personnel having no special technical skill is photographing, a photographic composition of appropriate sense of depth of foreground and background is not always guaranteed and can even finish in one with a poor perspective.
FIG. 3 shows an example of a conventional 3D photograph. Despite the fact that each of the frames of a negative are photographed with an appropriate spacial parallax, the right and left eyes of a observer will catch the image bands that are not neighboring and will not be able to appreciate the appropriate spacial parallax. If more than 4 image-bands are printed using a multiple of photographing stations from prepared negatives consisting of more than 4 frames, due to the fact that the view angle covered by a single image band is small, the right and left eyes of an observer will catch the image bands that are not neighboring depending on the observer's location, and that will result in an out-of-focus situation or a wrong vision.
If an object of poor perspective effect or a small spacial parallax is to be photographed, a 3D photograph of the object prepared with conventional printing methods will not sufficiently produce a three dimensional effect. The present invention thus has the objective of realizing a 3D photographic printing method, wherein a desired spacial parallax is obtained, said photographic method producing 3D photographs of excellent three dimensional effects.
Depending on the photographic object, not only the depths of the foreground and background, the relationship of the positions of the foreground object, the principal object and the background object will also be different, in addition the spacial parallaxes of the foreground, principal and background objects not being fixed.
If for instance, a composition of the principal object located in the foreground is to be photographed, despite the fact that the parallax between the principal object and the foreground object is slight, that between the principal object and the background object is extremely large. In conventional 3D photographic printing apparatuses, where a part of such a principal object is selected as the key-subject and exposure is performed so as to make such key-subjects definitely coincident, the parallax of the background object will become too large that an out-of-focus situation will arise in the background.
Contrarily, when a composition of the principal object located in the background is photographed, despite the fact that the parallax between the principal object and the background object is slight, that between the principal object and the foreground object becomes extremely large. When a part of such a principal object is selected as the key-subject and exposure is performed so as to make such key- subjects definitely coincident, the parallax of the foreground object will become too large that an out-of-focus situation will arise in the foreground.
When a prepared 3D photograph is viewed in a situation where the parallax is extremely large as above, it is only possible to grasp distinctively the neighborhood of the key-subject of the principal object, and as a whole, the photograph will lose its finish and three dimensional effect. The present invention has the objective of providing 3D photographs of excellent finish by obtaining a 3D photographic printing apparatus that takes account of the differences in the spacial parallaxes among the foreground object, the principal object and the background object.